Conventional driveline systems typically include shaft assemblies for delivering torque from a driving system, such as a motor or engine to a driven system, such as wheels or power equipment, which allows some relative axial movement between the driving and driven systems.
In a rear wheel drive motor vehicle, for example, a vehicle driveshaft or propeller shaft transmits torque from the transmission through a differential to the rear wheels of the vehicle, thereby causing the vehicle wheels to be desirably and selectively turned. The propeller shaft also dynamically compensates for the change or modification in the distance between the transmission and the differential that may occur when the vehicle is driven. Hence, the propeller shaft includes a portion or a member, which typically and telescopingly moves along the longitudinal axis of the propeller shaft in response to relative movement between the differential and the transmission, thereby allowing the propeller shaft to dynamically modify its length in response to the movement of the vehicle.
Such driveline systems often include an inner member or shaft having an outer surface with a splined portion and an outer member or sleeve having an inner surface with a splined portion. The splined portion of the shaft is capable of being slidably engaged in the splined portion of the sleeve to form a splined connection therebetween.
For a variety of reasons, primarily relating to the build up of tolerances between the shaft and sleeve, a mechanism must be provided for securing the sleeve and shaft together so that their splined portions will be snuggly engaged together. Furthermore, a build up of tolerances results in a partial misalignment of the rotational centers of gravity of the shaft and sleeve that must be compensated for by adding balancing weights to compensate for mass imbalance between the shaft and sleeve. Adding balancing weights increases both manufacturing time and cost.
In one known system, the removal of the slack between the sleeve and shaft can be accomplished by providing a radial preload between the shaft and sleeve to bias the splined portions into engagement. In such a system, the driveline assembly includes a spring disposed between a recessed portion of the male stub shaft and a splined portion of a female sleeve reacting between the male stub shaft and the female sleeve to apply a radial force on the male stub shaft to take up clearances between the two sets of splines.
While this solution provides for better engagement between the shaft and the sleeve, it has a significant shortcoming. The spring biases the sleeve and shaft system in a manner further displacing rotational centers of gravity, thereby requiring a significant amount of mass to dynamically balance the system. The additional mass adversely impacts efficiency.
Another known approach to engage the splined portions is to lengthen the shaft and sleeve so as to reduce the impact of the accumulation of tolerances. However, this arrangement adversely impacts both energy efficiency and space utilization.
Therefore, what is needed is a coupling system for a shaft assembly that will permit a more efficient coupling of a splined shaft with a spline sleeve.